); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I support what Rick has said about crystal ageing. I also work for an OCXO manufacturer, and will add my 2c worth.. Here are some points -
* Manufacturers do indeed have their own special techniques for minimizing ageing and numerous other quality related parameters. Cleanliness, quality and attention to process are very important. Many techniques will be specific to their own manufacturing process, and of course they are trade secrets. * Because many different ageing processes are involved, prediction of future ageing from past history is not in general reliable. A very good analogy is prediction of weather - to say that tomorrow's weather will be similar to today's is a fairly safe bet, but is no help in predicting the weather for next weekend! The same applies to good crystal oscillators - you can reasonably expect the rate of ageing next month to be closely similar to last month's, but the slight differences build up in extrapolation, and prevent long term prediction. Make your measurements, predict the trend, then do the same next month and note the differences. * It is very important to recognise the difference between INITIAL ageing (when a newly made crystal is first used) and long term ageing. Most users will never see initial ageing, as it takes place in the factory. Initial ageing is much more predictable, and the factory will monitor this and from this behaviour, within a week or so can predict when (if ever!) the device will be within specification and so ready for final calibration and delivery. I recommend reading the various papers on ageing published by the UFFC and others. Start with this fairly comprehensive and authoritative one: http://www.ieee-uffc.org/freqcontrol/vigaging91/aging.htm#CONTENTS 73, Murray ZL1BPU _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
